1. Field of the Invention
The present invention relates to hollow bats primarily for softball, and more particularly, to metallic and composite hard shell bats. Such bats typically include a metal outer shell which may be formed of aluminum or titanium alloy or other metals or of composite construction. As referred to herein, the terms xe2x80x9caluminumxe2x80x9d and xe2x80x9ctitaniumxe2x80x9d are intended to encompass the metals and alloys and mixtures of metals and alloys formulated for the manufacture of bat shells.
2. Prior Art
U.S. Pat. No. 5,676,610 to Bhatt et al. discloses a tubular bat having a sheet of metal, wound into a spiral spring, in contact with the inner wall of the barrel of the bat. Shear stresses are not transferred from the outer shell to the metal insert leaving the bat compliant.
U.S. Pat. No. 5,533,723 issued Jul. 9, 1996 to Baum discloses a composite bat having a wood veneer surface and intermediate composite layer bonded to a tubular core of composite or aluminum. The core may comprise a resilient urethane foam and a cavity may be left in the core in the hitting area and the cavity may be filled with less dense material. The core may vary in density over the length of the bat, preferably with a higher density section near the barrel end.
U.S. Pat. No. 5,511,777 to McNeely discloses a bat having a rebounding core therein. A resilient attenuator sleeve is compressed between the outer shell and an inner damper fashioned from brass or a similar material. The resilient attenuator sleeve may be fashioned from a polystyrene closed cell foam.
U.S. Pat. No. 5,460,369 issued Oct. 24, 1995 to Baum discloses a composite bat having a wood veneer surface bonded to a composite tubular core.
U.S. Pat. No. 5,458,330 issued Oct. 17, 1995 to Baum discloses a composite bat having a wood veneer surface and cavitied foam core.
U.S. Pat. Nos. 5,511,777 and 5,415,398 issued to Eggiman disclose tubular bats having a rigid outer shell and a tubular insert in the ball striking area, the insert being spaced from the outer shell and acting independently thereof which is said to increase bat compliance while moderately limiting denting of the barrel. This design, due to the gap between the insert and the outer shell, fails to transfer shear stresses from the outer shell to the insert.
U.S. Pat. No. 5,395,108 Souders et al. issued Mar. 7, 1995 is an example of a fiber reinforced composite shell bat filled with expansible urethane foam to develop compressive stresses between the foam and the outer shell.
U.S. Pat. No. 5,364,095 issued Nov. 15, 1994 to Easton et al. discloses a tubular metal ball bat internally reinforced with a carbon fiber composite layer in firm compressive engagement with the outer shell.
U.S. Pat. No. 5,114,144 issued May 19, 1992 to Baum discloses a composite baseball bat made to look like a wood bat by using a central core of foamed plastic or extruded aluminum covered with a layer of resin impregnated fiber knitted or woven cloth and a surface layer of longitudinally extending planks or strips of resin coated wood veneer.
The primary objective of the invention is to provide a more compliant lightweight yet strong and durable metal shell softball bat.
The present invention provides a ball bat comprising:
a) a rigid outer shell having a central axis and a handle and a barrel axially spaced from said handle;
b) a substantially cylindrical rigid insert in said barrel, said rigid insert being radially spaced from said outer shell; and
c) an elastomeric layer having a COR of not less about than 40% and outer and inner generally cylindrical surfaces respectively engaged in force transmitting relationship with said outer shell and with said rigid insert.